The present invention relates to a spinal implant having a unit structure that is printed by using a 3D printer, and more particularly, to a spinal implant having a unit structure printed by using a 3D printer, which is capable of implementing elastic force like the existing vertebrae while bone fusion is performed as well as a state in which the bone fusion is completed after a procedure to obtain superior procedure results.
A disc existing between vertebrae functions as a joint and plays very important roles for minimizing an impact applied to a spine while vertebral pulp accommodated inside the disc changes in position and shape according to the movement of the vertebrae.
The vertebral pulp is mostly moisture (water). When we get older, an amount of moisture gradually decreases, and thus, a buffer function of a disc is lost.
As a result, when an excessive pressure is applied to the fibers, backache may occur. Here, if the excessive pressure is continuously applied, the fibers may be seriously stretched or ruptured to push nerve roots placed at a rear side thereof, thereby causing pains of pelvis, legs, and the like.
Thereafter, a distance between the vertebrae gradually decreases, or the vertebrae are collapsed to cause various kinds of side effects such as vertebral deformation.
There is a method, in which an intervertebral fusion cage, so-called, a cage is inserted between two adjacent vertebrae after a disc between the damaged vertebrae is removed, as a method for treating diseases involved due to the disc.
That is, the cage recovers the distance between the vertebrae to its original distance between the two adjacent vertebrae, which corresponds to an original height of the disc, thereby recovering the vertebral function.
However, the general intervertebral fusion cage has a solid structure made of a metal material such as titanium or a titanium alloy. Thus, there is a limitation that facing surfaces of the vertebrae adjacent to each other subside by top and bottom surfaces of the age after the intervertebral fusion cage is inserted between the vertebrae to complete the procedure.
As an invention derived in view of the above-mentioned points, an intervertebral fusion cage utilizing various kinds of 3D printing techniques as illustrated in FIG. 11, which include “a method for producing a porous metal implant and a porous metal implant manufactured thereby (hereinafter, referred to as a prior art)”, which is disclosed in Korean Patent Publication No. 10-2016-0128236, has been developed.
Each of the intervertebral fusion cages manufactured by the prior art and the existing 3D printing manufacturing method illustrated in FIG. 11 has a mesh structure having a linear lattice shape on the whole so as to improve the bone fusion.
However, although all the intervertebral fusion cages manufactured by the existing 3D printing manufacturing method including the prior art has been done to some extent, there is almost no generation of elastic force for realizing a buffering effect with respect to a pressure and an impact due to a weight and a posture change of a person to be surgically operated (hereinafter, referred to as a subject).
Thus, the existing 3D printing manufacturing method, in which there is no elastic force in the process of performing the bone fusion after the procedure, i.e., until the bone fusion is completely performed, does not prevent the subsidence phenomenon that occurs on the facing surfaces of the vertebrae adjacent to each other.
In addition, after the bone fusion is completed, natural elastic force that absorbs an impact of the human body like the existing vertebrae is not provided.